Open access sleeve for heated fluid units

ABSTRACT

A series of implementations of open access sleeves for holding one or more closed containers of sterile fluid for use in medical procedures are disclosed. The open access sleeves may be adapted to provide heat to maintain the containers of sterile fluid above the ambient air temperature of the room. The provision of heat may be controlled by a control system. The control system may use a temperature measurement device to obtain a temperature representative of the container of sterile fluid and of the sterile fluid in the container. The access sleeve may be included in a device for maintaining an open volume of sterile fluid within a range of a target temperature to maintain the closed containers of sterile fluid at a temperature near target temperature for open volume of sterile fluid.

This application claims priority to co-pending U.S. patent applicationSer. No. 11/209,283 for Liquid Warming Device with Basin. Thisapplication claims priority to the priority applications for the '283application: A) U.S. Provisional Patent Application 60/603,957 forHeating Element for Liquid Warming Device filed Aug. 24, 2004; B) U.S.Provisional Patent Application 60/603,956 for Liquid Warming Device andControl System filed Aug. 24, 2004, and C) U.S. Design patentapplication Ser. No. 29/226,136 filed Mar. 24, 2005 for Hospital Basinwith Channel. All four of these applications are incorporated byreference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to improvements in methods and apparatus forheating of sterile surgical liquids. More specifically, this inventionrelates to devices used to keep sealed containers of sterile surgicalliquids at or near a desired temperature above the ambient airtemperature of the room. These devices may work in conjunction withanother heating system to maintain an elevated temperature of surgicalfluids in an open container such as a basin or cavity formed in asterile drape.

2. Background of the Invention

Devices for the heating of sterile surgical liquids are known in theart. In a wide variety of surgical procedures, sterile fluids are usedto irrigate the site of the surgery. It is important that thetemperature of the fluids used be strictly controlled. As the portion ofthe brain that regulates body temperature is shut down with anesthesia,it is important that the introduction of sterile fluids does not coolthe body core temperature. Clinical studies have indicated that a rangeof adverse consequences arise from a change in body core temperature aslittle as one to three degrees Celsius. The adverse consequences frommild perioperative hypothermia include hypertension and increasedvascular resistance, cardiac events, coagulopathy, an increase risk ofsurgical wound infections, and delays in the body's ability to removedrugs from its systems. An additional potential adverse consequence isshivering that may increase metabolic rate up to 500% and thus increasedemands for oxygen and the need to clear carbon dioxide. This list ofcomplications is by no means exhaustive, but it highlights the criticalimportance in controlling the body core temperature. Careful control ofthe temperature of sterile irrigation fluids is an important part ofcontrolling body core temperature.

Co-pending and commonly assigned U.S. patent application Ser. No.11/209,283 for Liquid Warming Device with Basin discloses variousapparatus configurations and control schemes to precisely control thetemperature of a sterile fluid in an open container such as a surgicalbasin or a surgical drape covering a cavity in a fluid warming device.

SUMMARY OF THE DISCLOSURE

The deficits in the prior art are addressed by the addition of one ormore access sleeves to devices for maintaining open volumes of sterilefluid at an elevated temperature. Having access sleeves maintain ormodify the temperature of sterile fluid in closed containers stored inthe operating room allows the addition of sterile fluid from the closedcontainers to the open volume of heated sterile fluid without greatlychanging the temperature of the new expanded volume of sterile fluidfrom a target temperature for the open volume of sterile fluid. While itmay be convenient to have an access sleeve in the same device thatmaintains the open volume of sterile fluid at an elevated temperature,one or more access sleeves can be implemented in an access sleevecabinet. The access sleeves may be implemented in a number ofconfigurations. It may be useful to slope the access sleeve to allowfluids to drain out the open end of the access sleeve. It may be usefulto slope the access sleeve so that containers tend to move to aparticular portion of the access sleeve. If the access sleeve is slopedtowards the open end, it may be useful to have protrusions that extendto impede the closed containers from slipping out of the open end of theaccess sleeve.

The access sleeve may be sized to receive more than one container ofsterile fluid. The access sleeve may be configured to have two open endsso that containers of sterile fluid may be introduced or removed fromeither end.

The access sleeve may have heating elements that are controlled by acontroller. The controller may act at least in part on a temperaturemeasurement taken from a temperature sensing device adapted to obtain atemperature indicative of the temperature of the container of sterilefluid.

Temperature indicators may be provided that provide either a qualitativeor quantitative indication of the temperature of the container ofsterile fluid. The user may be allowed to alter the set pointtemperature for the control system to alter the target temperature forthe closed container of sterile fluid. A series of implementations ofopen access sleeves for holding one or more closed containers of sterilefluid for use in medical procedures are disclosed. The open accesssleeves may be adapted to provide heat to maintain the containers ofsterile fluid above the ambient air temperature of the room. Theprovision of heat may be controlled by a control system. The controlsystem may use a temperature measurement device to obtain a temperaturerepresentative of the container of sterile fluid and of the sterilefluid in the container. The access sleeve may be included in a devicefor maintaining an open volume of sterile fluid within a range of atarget temperature to maintain the closed containers of sterile fluid ata temperature near target temperature for open volume of sterile fluid.

Other systems, methods, features, and advantages of the invention willbe or will become apparent to one with skill in the art upon examinationof the following figures and detailed description. It is intended thatall such additional systems, methods, features, and advantages beincluded within this description, be within the scope of this invention,and be protected by the accompanying claims.

BRIEF DESCRIPTION OF THE FIGURES

The invention can be better understood with reference to the followingfigures. The components of the figures are not necessarily to scale,emphasis being placed upon illustrating the principles of the invention.Moreover, in the figures, like reference numerals designatecorresponding parts through the different views.

FIG. 1 is a perspective view of one implementation of a liquid warmingdevice.

FIG. 2 illustrates the various components associated with providing acontrolled amount of heat to maintain the temperature of the sterilefluid.

FIG. 3 illustrates an implementation in which two access sleeves 400 and450 are provided for the local maintenance of containers of sterilefluid at a desired temperature.

FIG. 4 is an exploded diagram of components from the access sleeve 400shown in FIG. 3.

FIG. 5 is a graph of heat output as a function of temperature for anillustrative example of heat cable.

FIG. 6 illustrates various configurations of devices including heataccess sleeves with a variety of slopes towards the open end of theaccess sleeve.

FIG. 7 illustrates a cross section of the relevant portion of animplementation of a device to expose two access sleeves 800 and 850.

FIG. 8 shows a pair of dual-ended access sleeves 900 and 950 with slopedsleeve bottoms 912 and 962.

FIG. 9 is a perspective view of a device having access sleeves that areintended to maintain containers of sterile fluid in a substantiallyupright orientation.

FIG. 10 shows access sleeve cabinet 1100.

FIG. 11 is a graph to explain a cascade control scheme for controllingthe application of heat.

FIG. 12 shows an implementation a pair of V-shaped walls 1212 and 1216.

FIG. 13 is a front view of an access sleeve having a bottom surface withan arc that is similar to the radius of bottles used in the accesssleeve.

DETAILED DESCRIPTION

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in order to disclose selectedembodiments. This invention may, however, be embodied in many differentforms and should not be construed as limited to the embodiments setforth herein; rather, these embodiments are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of the invention to those skilled in the art. Like numbers referto like elements throughout.

FIG. 1 is a perspective view of one implementation of a liquid warmingdevice 100. The liquid warming device 100 has a top surface 104 adaptedto receive a sterile removable basin 108 with a lip 112. The sterileremovable basin 108 is combined with a sterile drape 116 with an openingso that the bottom of the sterile removable basin 108 extends throughthe opening in the sterile drape 116 to engage with the liquid warmingdevice 100. Co-pending and commonly assigned U.S. patent applicationSer. No. 11/209,283 for Liquid Warming Device with Basin (incorporatedby reference above) describes desirable interactions between sterileremovable basin 108 and the liquid warming device 100 to detect thepresence of an appropriate sterile removable basin 108 and to sense thetemperature of sterile fluid 120 through the use of a thermocouple well(not shown here).

FIG. 2 illustrates the various components associated with providing acontrolled amount of heat to maintain the temperature of the sterilefluid 120. The sterile fluid 120 is inside modified basin 304 withintegral thermocouple well 312 and temperature sensor 316. Based on theinput from controller 320 to relay 324, the basin heater 362 selectivelyapplies heat that is transferred to the basin 304 and the sterile fluid120. The controller 320 is using a dual set point control scheme basedon the target temperature 352, the temperature sensed at 316representative of the temperature of the sterile liquid 120 and thetemperature measured at temperature sensor 366 representative of thetemperature at the heater 362. Other control schemes may be used thatmay not use the temperature sensor 366.

The fluid warming device 300 has a main on/off switch 336. Some heatingelements come with a mechanical thermostat 344 such as a bimetallicthermostat to provide a secondary protection against a failed controlsystem. This second mechanical thermostat 344 acts as a switch to shutoff the heater if the temperature exceeds a set temperature. Thismechanical thermostat 344 should be set to a temperature that is lowenough that the mechanical thermostat 344 opens before the heater 362may overheat an empty basin 304. For example a mechanical thermostat setfor 220 degrees Fahrenheit might be acceptable for use with a basincapable of withstanding permanent exposure to a 300 degree Fahrenheitheat source.

In this implementation, a modified sterile drape 310 is connected tosome combination of the upper rim of the basin 304 or its outside wallso that the basin 304 extends down through the hole in the surgicaldrape 310. As the modified sterile drape 310 does not run along thebottom of the basin 304, the drape 310 does not interfere with theinteraction of the thermocouple well 312 and the control system. Nordoes the sterile drape 310 get between the bottom of the basin 304 andthe heat coming from heater 362 to the bottom of the basin. The drapebasin combination would typically be combined together as part ofpreparing a surgical kit and the drape would encircle the basin bottomwith the remainder of the drape folded or pooled in the cavity of thebasin so that the basin may be placed into the fluid warming device andonce properly positioned, the drape may be unfolded from the basin tocover the top and upper sides of the fluid warming device to maintain asterile field.

The interaction between the sterile drape 310 and the removable basin304 may be a simple interference fit such that the basin once insertedinto a hole in the drape stretches the drape so that the drape staysattached to the basin sufficiently for it to maintain the sterile field.Alternatively, the drape may be bonded to the outer wall of the basin orto the underside of the rim of the basin.

FIG. 2 shows drape 310 extending downward to cover the components inFIG. 2. This is illustrative of the point that the drape is used tomaintain the sterile field, but one of skill in the art will recognizethat individual components shown in FIG. 2 are apt to be inside ahousing and not in direct contact with the drape. One exception is thetops of the indicator lamps 328 and 332 (discussed below) that mustremain visible through the drape as discussed in detail below. Also asdiscussed below some controls may be placed outside of the sterile fieldand thus located below where the drape ends on the liquid warmingdevice.

The user may alter a target temperature 352 for the fluid through theuse of input keys 340. The term “user” refers to the end user of thedevice in the operating room. There may be a set of users of the devicein the operating room including those working in the sterile field andthose working outside of the sterile field. Medical equipment is alsotested and serviced by technicians and engineers. The technicians andengineers that test and service the equipment are not users as they haveaccess to tools, documentation, and controls that are not accessible tousers.

The target temperature 352 and the current temperature of the fluid maybe displayed on a display 348. The input keys 340 and the display 348 inone implementation are placed low on the housing so that thesecomponents are below the drape 310 and outside the sterile field. One ofskill in the art will recognize that special window may be placed in thedrape or the drape may be made of material with optical properties thatallow a standard LED display to be read through the drape.

In one embodiment, two visual indicators are provided that may be seenfrom a distance to allow those participating in the surgery to check thetemperature status of sterile fluid 120 from afar. When theAt-Temperature indicator lamp 328 is lit, this conveys that the fluidtemperature of sterile fluid 120 is at the target temperature or withina certain tolerance of that target temperature. In contrast, when theOut-of-Range indicator lamp 332 is lit, it indicates that the liquidwarming device 300 has power and the main on/off switch 336 is turned onbut the sterile fluid 120 is not within a certain tolerance of thetarget temperature. In one implementation, light 332 is not lit unless alimit switch indicates that a basin is present.

In this embodiment, a single Out-of-Range indicator is sufficient as thestaff would typically know whether they had added cool water or hotwater to the basin. In the event that the staff was not sure whether thetemperature was above or below the desired range, the specifictemperature may be obtained from the display 348. This gives the staffthe information necessary to make an informed quantitative decision touse out-of-range fluid if the particular intended use of theout-of-range fluid would be acceptable. As noted below, one of skill inthe art may appreciate that the Out-of-Range indicator may be revised tobe two indicators: an above range indicator and a below range indicator.

A preferred embodiment uses a green lamp for At-Temperature and either ared lamp or most preferred, a yellow lamp for Out-of-Range. As thepreferred embodiment separates the liquid warming device from thesterile field through the use of the sterile drape 310, the indicatorlights selected (size, brightness, degree of protrusion from thesurface) must be suitable for providing an adequate visual signal eventhrough the drape material which for some drapes is not fullytransparent. LED lights may be suitable for at least some drapematerials. Ideally the light source should be of the type that projectslight towards the drape as this helps make the visual indicator visible.While not preferred, the lights may be made more visible by placing awindow of substantially transparent material in the drape so that whenappropriately placed on the fluid warming device the window is placedover the visual indicator lights.

The portion of the indicator light assembly that comes in contact withthe surgical drape may operate at a temperature that may be maintainedin contact with a surgical drape for an extended period of time withoutdamaging the surgical drape. An extended period of time would mean 24hours of contact without damaging the drape.

One may provide further detail by using separate indicator lamps forabove the temperature target range and one for below the temperaturetarget range. Perhaps, blue for too cold and red for too hot. Likewise,one may add additional indicator lamps to distinguish between close tothe target temperature range but still out of range from an indicationthat the current fluid temperature is further from the targettemperature range. For instance an implementation may use a yellow lampfor close but not quite in range. One of skill in the art will note thatflashing lights may be used to convey something different from constantlights. For example a flashing the In-Range and Out-of-Range lightsmight convey that the temperature is almost in-range.

Another alternative for indicator lights is to provide one light toindicate that the warming device is turned on and a second light toindicate that power is currently being applied to the heater 362. Whenthe fluid temperature is significantly below the target temperature, theheater-on light will be lit for an extended period of time. As thetemperature of the sterile fluid approaches the target temperature, theheater will be turned on and off thus causing the heater-on light toturn on and off. Contingent on the control scheme implemented to controlthe heater, the steady state operation of the control system to maintainthe temperature of the sterile fluid 120 may be frequent switching ofthe heater on and off.

Optionally, the temperature of the sterile fluid may be printed alongwith the time or alternatively this information may be stored forprinting later. In either case, a history of the temperature over timemay be used in connection with other surgical records to document thatthe sterile fluid was at an appropriate temperature when used.

As evidenced by the details set forth above, a great deal of care andattention is devoted to measuring the temperature of the sterile fluidand maintaining the sterile fluid in a particular narrow temperaturerange through the controlled application of heat to the sterileremovable basin 304.

The sterile fluid 120 is in the operating room to be used in a varietyof irrigation, lavage, or other medical procedures. Thus, the volume ofsterile fluid is depleted and must be periodically replenished. Sterilefluids for placement in basins for use in medical procedures typicallycome in plastic bottles with a substantially square cross section. Bulkstorage warmers may be used to heat large quantities of such bottles tobring the sterile fluids to a particular temperature that is close tothe desired temperature for a variety of procedures (such as bodytemperature or slightly above body temperature). These bulk warmers aretypically located outside of any one surgical room so that the heatedsterile fluid may be used by a several different surgically rooms. Whileit is convenient to have one or more un-opened bottles 370 of sterilefluid 220 placed in a surgical room in anticipation of the need toreplenish the sterile fluid 120 removed from the basin, as time passes,the temperature of the heated sterile fluid 220 in the un-opened bottle370 drops as the sterile fluid 220 cools in response to the ambient airtemperature.

Replenishing the depleted supply of heated sterile fluid 120 in thebasin 304 (FIG. 2) with sterile fluid 220 from the bottle 370 may causea drop in the temperature of the sterile fluid 120 in the basin 304 tothe extent where the temperature of the sterile fluid 120 in the basin304 is no longer in the desired narrow temperature range. At this point,the medical staff is faced with the choice of waiting until the heater362 acts to heat the volume of sterile fluid 120 back to within thedesired narrow temperature ranger or use sterile fluid that is coolerthan desired.

Alternatively, although probably less frequently, it is possible that abottle 370 of sterile fluid 220 obtained from the common bulk heater maybe at a temperature that is above that desired for this particularprocedure so that adding this sterile fluid 220 brings the temperatureof the sterile fluid 120 in the basin 304 above the desired narrowtemperature range. Again the medical staff would need to choose betweena delay in the procedure, using sterile fluid 120 from the basin 304that is above the desired temperature, or perhaps finding a bottle ofsterile fluid that has not yet been placed in the common bulk heater andusing this cool water to quickly drop the temperature of the sterilefluid 120 in the basin 304.

Thus, it may be useful to have the ability to place one or more bottles370 of sterile fluid 220 in a local warming unit so that bottles may bemaintained or conditioned to be within or close to the desired narrowtemperature range around a set point 352 so that mixing of sterile fluid220 to replenish a depleted volume of sterile fluid 120 in the basindoes not move the aggregate fluid temperature out of the desired range.Note that while the contents of the bottle are sterile, the exterior ofthe bottle is not considered sterile and would not have to be storedwithin a portion of the sterile field.

Open Access Sleeve for Heated Fluid Units.

FIG. 3 illustrates an implementation in which two access sleeves 400 and450 are provided for the local maintenance of containers of sterilefluid at a desired temperature. While FIG. 3 shows an implementationwith two access sleeves, the present invention may be implemented as anynumber of one or more access sleeves.

Bottle 370 of sterile fluid 220 is inserted into a cavity 404 in accesssleeve 400. As described below, the bottom surface of the access sleeveis tilted so that the bottom front of the cavity is below the bottomrear of the cavity. A range of slopes may work for the bottom surface.The slope should be sufficient so that any liquid that is on the outsideof the bottle 370 or leaks from the bottle 370 flows forward and out ofthe access sleeve. Thus a slope of as little as 1 degree may suffice buta slope of approximately 5 degrees or more does a better job at drainingoff any fluid. A protrusion 408 extends upward from near the front ofthe open access sleeve 400 to resist the forward movement of the bottle370 from sliding out of the access sleeve 400. (The protrusion foraccess sleeve 450 is not visible as it is covered by the top portion ofthe IV bag of sterile fluid in that access sleeve.) The height of theprotrusion 408 needed to retain the bottle 370 is primarily a functionof the slope of the bottom surface of the cavity but will be influencedby the coefficient of friction between the bottle and the bottom of thecavity and the geometry of the bottle. The slope of the cavity used inthis example is approximately 10 degree. Slopes up to 15 and even 20degrees may be used with adequate protrusions.

A temperature sensor is used to detect the temperature of the bottle370. The temperature of the bottle 370 is displayed in the temperaturedisplay 412. It is preferred to have a separate temperature sensor anddisplay for each access sleeve. (note that the bottle 370 and the bag470 are at slightly different temperatures as one may have come from awarmer storage cabinet than the other, or the bottle may have had moretime to reach a target temperature of 104 degrees Fahrenheit than hasthe bag.)

Access sleeve 450 has a separate temperature sensor that senses thetemperature of the container placed in that access sleeve and displaysthat temperature in temperature display 462. To the extent that arelationship is known between the temperature measured by thetemperature sensor and the average temperature of the sterile fluid inthe container, a correction may be applied to the measured temperaturesuch that the corrected temperature is displayed. For example, it may bethat a temperature sensor measuring the temperature between the heatedbottom wall of the access sleeve and the wall of the container may bewarmer than the precise temperature of the sterile fluid as a portion ofthe container is in contact with ambient air at the open end of theaccess sleeve.

As shown in FIG. 3, medical staff may find it convenient to place a bagof sterile fluid that will be used in a manner other than emptied intobasin 108 (See FIG. 1). For example the contents of the bag of sterilefluid may be introduced by a gravity based IV.

A preferred placement for the temperature sensor is on the bottomsurface of the cavity. To the extent that a common brand of bottledsurgical fluid has a deep concavity (including a circumferential ridge)that would impede good contact between the temperature sensor and thebottle, the distance between the temperature sensor and the protrusionmay be adjusted so that a portion of the bottle that is relatively flatwould be positioned over the temperature sensor. Having a significantslope to the bottom surface of the cavity helps ensure that the bottleslides forward to make contact with the protrusion so that the bottleassumes a repeatable position in the access sleeve. The temperature ofthe exterior of the container is used as a proxy for the temperature ofthe sterile fluid in the container. This assumption is not perfect asthe temperature of the container surface on the bottom wall of theheated cavity may be slightly warmer than the average temperature of thefluid in the container while the fluid is being heated but shouldeventually be close as the fluid reaches its target temperature.

FIG. 4 is an exploded diagram of components from the access sleeve 400shown in FIG. 3. Protrusion 408 may be affixed to the access sleeve face504. The access sleeve cavity is defined in part by perimeter container508 that receives temperature sensor insulator 512 and finishing plug516. Perimeter container 508 in this example fits into the back of theaccess sleeve face 504 and may be affixed by connectors (not shown) thatconnect the sides and top of the perimeter container 508 to the back ofthe access sleeve face 504. The temperature sensor insulator 512 isintended to isolate the finishing plug 516 and the temperature sensor(not shown) from the temperature of the access sleeve perimetercontainer 508 so that the temperature sensor responds to the temperatureof the container of sterile fluid.

Finishing plug 516 is ideally made of metal or another good thermalconductor to allow the thermistor placed in contact with the undersideof the finishing plug 516 to sense the temperature of the container incontact with the top of the finishing plug 516. One of skill in the artwill recognize that the thermistor or another temperature sensing devicemay adapted to be positioned to make contact with the container directlyrather than through a finishing plug.

In this example, heat cable assembly 520 forms a helix around theperimeter container 508 and is enclosed within shield 524. The heatcable assembly 520 is connected to power at connector 528. The exampleshown in FIGS. 3 and 4 uses approximately six feet of 10/watt per footself-regulating heater cable (described below).

The access sleeve is insulated by rear insulator 540, top insulator 544,bottom insulator 548, right side insulator 552, and left side insulator556. The temperature display 412 is composed of display 560 and lens 564affixed by adhesive frame 568. The rear insulator 540 may be connectedto either short bracket 572 or long bracket 576 depending on whether itwill be the lower or upper access sleeve. The specific geometry of thesebrackets are not central to the present invention. One of skill in theart will be able to provide an appropriate bracket to connect the accesssleeve to connection points in the device.

While more sophisticated control schemes may be employed to control theoperation of the heat cable assembly 520, a sufficient and costeffective control scheme is to provide power to the heat cable assembly520 whenever the temperature sensor senses a temperature two degreesbelow the set point for the access sleeve. When sensing that thetemperature is two degrees below the set point, full power is applied tothe heat cable for that access sleeve until the temperature reaches theset point at which time power is no longer applied to the heat cable.Each heat cable is independently controlled based on the temperaturereported from the temperature detector in the sleeve.

Heat cables are available that provide decreased heat output per linearfoot of heat cable based on the temperature of the heat cable. Oneexample is Nelson™ Type LT Self Regulating Heater Cable available fromNelson Heat Tracing Systems of Tulsa Oklahoma (www.nelsonheaters.com).

Using a heat cable makes the heating system effectively self-regulatingand makes it unnecessary to have a secondary thermostat to remove powerfrom the heat cable in the event of a failure of the control system.This type of heat cable varies the heat about based on the localtemperature of the heat cable so the system compensates to resist thecreation of hot spots as the cable in a section that is better insulatedor having a more dense allocation of heat cable will provide less heatper foot than another section of heat cable facing cooler operatingconditions. An example of the heat output as a function of temperatureis shown in FIG. 5. Response curve 600 shows the decrease in watt outputper linear foot of heat cable as the temperature of the heat cableincreases. The response curve 600 intersects zero watts per linear footat point 604 indicating that the heat cables are incapable of providingadditional heat as the heat cables reach approximately 170 degreesFahrenheit. Thus, the temperature of the access sleeve cannot exceed 170degrees even if the thermal sensor or control system should fail. At 70degrees Fahrenheit, which is approximately the ambient temperature of anoperating suite, the heater cable assembly depicted in FIG. 5 wouldproduce approximately 8 watts/linear foot to quickly heat the accesssleeve.

Ideally, the power supply is adequate to allow simultaneous operation ofthe heater cable assemblies for all access sleeves. While it is moreefficient to not heat an empty access sleeve, the example of an accesssleeve shown in FIGS. 3 and 4 do not have a container detector and theheater cable assemblies continue to heat the access sleeve.

The set point for the access sleeve temperature may be readilymanipulated by the end users through input devices placed on theexterior of the device analogous to input keys 340 described inconnection with input of a set point for the heated basin. The set pointfor the temperature setting for the access sleeves may also be adjustedthrough a variety of means known in the art including but not limited tovarying the position of a rheostat, providing a program instruction tothe control system through a data connection, dip switch settings, orthe replacement of a Read Only Memory. These manipulations would not bemade by end users of the heated sterile fluid but by engineers andtechnicians with responsibility for testing, calibrating, and servicingthe equipment.

The temperature detector used in the example shown in FIGS. 3 and 4 is athermistor. A wide range of temperature detection devices may beemployed by one of skill in the art including such options asthermocouples and RTD. Thermistors provide high sensitivity, goodtransient response and are relatively inexpensive. This combination offeatures makes thermistors well suited for this application.

Alternative Embodiments

While the illustrative example provided above was useful in conveyingaspects of the present invention, the illustrative example is by nomeans the only way to benefit from the teachings of the presentapplication.

Alternative Heating Patterns.

FIG. 4 illustrates the use of a helical pattern for the heating elementsuch that the heating element is in proximity to all the walls betweenthe back wall and the open front of the access sleeve. Others may chooseto apply heat to only the bottom wall or to some other subset of wallsbetween the back wall and the open front. The back wall may be heated aswell. If a heating pattern is selected that does not place heatingelements in proximity to the temperature detector, then it becomes lessimportant that the temperature detector is thermally insulated from thethermally conductive wall as a heating element that is not near thetemperature detector is less likely to impact the measurement of thethermal detector even if the thermal detector is not isolated from thethermally conductive wall of the access sleeve.

The one or more heating elements used to apply thermal energy to thewalls of the access sleeve do not need to be in direct contact with thewalls. In order to promote effective transfer of heat between the one ormore heating elements and the walls, each heating element may be placedin thermal contact at least a portion of the set of walls by providing athermally conductive path (that is at least one path devoid of asignificant thermal insulator) between heating element and the wall.

Another heating strategy that may be employed isolates one of the wallsfrom the other walls defining the access sleeve using a thermalinsulator of adequate thickness to substantially isolate the isolatedwall from the adjacent walls. In this strategy, the isolated wall is notplaced in thermal contact with a heating element but a temperaturedetector is placed in thermal contact with the isolated wall. Theisolated wall is created to be a thermal conductor so that thetemperature of the sterile fluid is available to the temperaturedetector through the container of the sterile fluid when a container ofsterile fluid is placed in direct or indirect thermal contact with theisolated wall.

Alternative Protrusions.

The example set forth above uses one protrusion in the center of theaccess sleeve. One of ordinary skill in the art will recognize that aset of two or more protrusions may be used or that a lip from one sideof the sleeve opening to another may be used. As the example set forthabove anticipates that any excess fluid will flow out of the opening ofthe access sleeve based on the slope of the bottom of the access sleeve,the choice of protrusions should not prevent the flow of water out ofthe access sleeve. One of skill in the art will recognize that there aremany options for achieving the dual objectives of retaining thecontainer of sterile fluid against the pull of gravity and allowingfluids to drain out of the access sleeve. The one or more protrusion mayhave fenestrations to allow the flow of water through the protrusionwall or the protrusions may be angled slightly so that fluids may runalong the base of the protrusion and still flow downward towards theopening in the access sleeve.

A gutter indentation behind the one or more protrusions may be connectedto a drain hole that leads to either an internal container or to thefloor. However, a drain passage may be deemed undesirable by somedesigners as adding an internal drain adds another cost to theconstruction of the device and may be blocked by debris lodged in theinterior of the drain passage.

Configurations without Slopes to Drain to the Front of the Sleeve.

The examples given above include a discussion of an advantage fromhaving a slope running from the back of the sleeve cavity to the frontof the open sleeve so that any fluids that may be on the exterior of thecontainer or that leak from the container flow to the front of thesleeve and out of the sleeve. While this is advantageous for someapplications, the invention is not limited to this configuration.

FIG. 6 illustrates various configurations that while not exhaustive,point out the range of possible arrangements for heating containers ofsterile fluid. The goal is to discuss the placement of the componentsrelevant to this particular discussion. FIG. 6 does not show all therelevant components that are discussed in other figures of thisapplication. FIG. 6A illustrated the concept of having two downwardlysloping sleeves represented here by sleeve bottoms 620 and 650. Near thefront of the sleeves are protrusions 624 and 654. As the containers thatare to be placed in these sleeves may vary in length, the temperaturesensors 628 and 658 are located in the half of the sleeve closer to thefront of the open sleeve.

FIG. 6B shows sleeve bottoms 670 and 690 sloping away from the openfront towards the closed back of the sleeve. As the slope is away fromthe open front, protrusions are not needed to retain the closedcontainers. As the length of the containers that may be placed in thesleeves may vary, it may be advantageous to place the temperaturesensors towards the back of the sleeve. Optionally, a drain gutter 680sloped to a drain hole 684 may be added in the back of the heatedsleeve.

FIG. 6C represents a cross section taken through the relevant portion ofthe device so that the access sleeves may be seen. More specifically,FIG. 6C shows a pair of sleeve bottoms 700 and 710 that are essentiallyflat between the front opening of the sleeve and the closed back. Aprotrusion 704 may be added to help retain containers of sterile fluidwhile the unit is moved from place to place as the unit containing thesleeves may be mounted on wheels. Temperature sensor 708 and 718 may beplaced towards the middle of the length of sleeve bottoms 700 and 710 asthe position of a container in the horizontal sleeve may be eithertoward the front of the sleeve or towards the closed back of the sleeve.

Dual-Ended Access Sleeves.

FIG. 7 illustrates a cross section of the relevant portion of the deviceto expose two access sleeves 800 and 850. These access sleeves do nothave a back wall as they continue from one end of the device to theother. Optionally, these access sleeves may have protrusions 804, 808,854, and 858 since it is possible that the act of placing the containerof sterile fluid 896 in one end of dual-ended access sleeve 850 mayinclude pushing against previously inserted container of sterile fluid892 until container of sterile fluid 892 stops against protrusion 854.

Optionally, the sleeve floor 812 or 862 may be essentially horizontal.While a dual-ended access sleeve may be sized so that it accommodatesone, two, or more containers of sterile fluid (such as bottles shownhere), many designers will find that selecting a length appropriate fortwo containers is a desirable choice. If adopted for maintaining twocontainers per sleeve, then one option for implementing the presentinvention is to effectively have two separate access sleeves joinedwhere the closed back of the access sleeve would otherwise be. In such asituation, the temperature sensor 816 may provide a temperature readingthat is displayed on temperature indicator 824 and used as an input inregulating the application of heat on that portion of the dual-endedaccess sleeve. Likewise, temperature sensor 820 provides a temperaturereading displayed on temperature indicator 828 and the sensedtemperature is used as in input in regulating the application of heat onthat portion of the dual-ended access sleeve. Optionally, a portion ofthe sleeve may not be heated by either the heater regulated bytemperature measured at temperature sensor 816 or by a heater regulatedby the temperature measured at temperature sensor 820 if it isanticipated that this middle portion 832 of the dual access heatersleeve will not normally have a container of sterile fluid positionedthere.

FIG. 8 shows a pair of dual-ended access sleeves 900 and 950 with slopedsleeve bottoms 912 and 962. The lowest points 932 and 982 of the slopedsleeve bottoms is somewhere between the two open ends to the dual-endedaccess sleeves 900 and 950. As with the dual-ended access sleeve shownin FIG. 7, the sleeve may be created to accommodate two bottles ofsterile fluid (such as 990, 994, and 998) (or two containers of someother type).

With sloped sleeve bottoms 912 and 962, the containers will tend to movetowards the low points 932 and 982. The actual position of the containermay vary slightly depending on whether the dual-ended access sleeve iscurrently holding one or two containers. Thus, container 990 has slidfurther into dual-ended access sleeve 900 than has container 994 indual-ended access sleeve 950 as dual-ended access sleeve 950 has asecond container 998.

The temperature sensor 916 may be used to provide the temperaturedisplayed in temperature indicator 924 and as an input to a controlleroperating the heating element providing heat to the end of thedual-ended access sleeve having temperature sensor 916. Likewise,temperature sensor 920 may be used to provide the temperature displayedin temperature indicator 928 and used as an input to a controlleroperating the heating element providing heat to the end of thedual-ended access sleeve having temperature sensor 920.

Dual-ended access sleeve 950 differs from dual-ended access sleeve 900in that sleeve ceiling 986 has a downward slope and sleeve ceiling 936is substantially horizontal. One of skill in the art may appreciate thatif the ceiling contained a portion of the heating system, then sleeveceiling 986 would place the portion of the heating system ceiling closerthe container 994 and 998, than is the case with ceiling 936 andcontainer 990. Even if the ceiling did not have a portion of the heatingsystem, some designers may prefer to reduce the volume of air in thedual access heater sleeve by sloping the ceiling.

While not shown here, one of skill in the art may appreciate that twoaccess sleeves with sloped bottoms running from the interior of thedevice to the access sleeve opening may be positioned contiguous to oneanother so as to form a dual-ended access sleeve with a high point inthe interior of the device rather than a low point as shown in FIG. 8.

While not shown here, one of skill in the art may appreciate that twoaccess sleeves may be positioned with essentially one downward slopefrom the upper opening to a second lower opening. In thisimplementation, containers placed into the upper opening are gravity fedtowards the lower opening and may be retained by one or more protrusionsextending from near the lower opening. If two or more temperaturesensors are used they may be placed along the access sleeve based on thelength of the primary container type anticipated for use in that accesssleeve.

Access Sleeves for Substantially Vertical Storage of Containers.

The examples provided above have shown the containers of sterile fluid,such as bottles or bags, to be substantially horizontal. An advantage ofsuch an orientation is that the opening of the access sleeve is smallrelative to the overall size of the container, which makes it easier tokeep the container warm.

An alternative type of access sleeve is shown in FIG. 9. In FIG. 9,liquid warming device 1000 has a top surface 1004 adapted to receive asterile removable basin (not shown) in a basin cavity 1008. The sterileremovable basin may be placed through a corresponding opening in a drape(not shown) so that the combination of the sterile basin and the drapeform a barrier between the sterile field and the upper surfaces of theliquid warming device. Indicator lights 328 and 332 may interact withthe control system to provide the user a visual indication whethertemperature sensor (not shown) located beneath the sterile removablebasin indicates that the sterile fluid is within a desired range oftemperatures. As noted above, the set of indicator lights may be done ina variety of ways and may involve more than two indicator lights. (Onemay also use just a single indicator light, perhaps using patterns offlashing lights, to provide an indication of whether the temperaturesensor is sensing temperatures that indicate that the sterile fluid iswithin a specified range of temperatures.) The indicator lights 328 and332 are adapted so that they may be viewed through the sterile drape.Alternatively, the sterile drape may have low opacity or transparentwindows that overlay the indicator lights 328 and 332.

Liquid warming device 1000 has a pentagonal top and a pentagonal base1012. The pentagonal base 1012 has one access sleeve per pentagonal sideon three sides of the liquid warming device 1000. Access sleeves 1020and 1040 are visible from this view and a portion of the access sleeveon an adjacent face is visible as well. The two sides not visible inthis view have access panels for assembly and maintenance. Access sleeve1020 has a set of walls 1024 forming a defined perimeter and a back wallto define the cavity of the access sleeve 1020. The perimeter walls havean integrated frame 1028 that rests against the exterior wall of theliquid warming device pentagonal base 1012. The container of sterilefluid 390 fits within the cavity of the access sleeve 1000. The bottomof the sterile container 390 rests on the bottom face of the accesssleeve that may be sloped towards the center of the liquid warmingdevice so that the container of sterile fluid rests against the backwall of the access sleeve 1020. If the slope of the bottom face of theaccess sleeve is not discernibly sloped downward towards the centerlineof the liquid warming device 1000, then some users may prefer that theliquid warming device have one or more protrusions 1044 for each accesssleeve to help retain the container of sterile fluid 390 as the liquidwarming device 1000 is moved or bumped.

The liquid warming device 1000 was built without temperature sensorsassociated with the individual access sleeves. Rather than an activecontrol system with a feedback loop, this device uses a simpler solutionthat is the constant application of a small amount of heat to each ofthe access sleeves. Containers of sterile fluid taken from bulk heatingcabinets and placed into mildly heated access sleeves cool down at amuch slower rate than bottles placed on an unheated countertop. Theamount of heat delivered to the access sleeves may be adjusted bycontrols inside the device so that the heat applied to an access sleevewith a container of sterile fluid does not get heated above the upperrange of the desired temperature range for the sterile fluid, even whenthe ambient temperature is at the upper range of the allowabletemperatures. Thus if the operating room is normally operated at 70degrees but the operating room is qualified for operation up to 80degrees, then the heater (or heaters) for the access wells is adjustedso that a bottle containing sterile fluid at the upper range of desiredtemperatures (for example 104 degrees Fahrenheit) will not increase intemperature even when the heat is applied for an extended period of timein a 80 degree room.

Liquid warming device 1000 has temperature indicator 1032 and input keys1036 for monitoring the temperature obtained from the temperatureindicator located near basin cavity 1008 and for changing the set pointfor the target range for the temperature of the sterile fluid placed inthe basin that is placed in the basin cavity 1008. The temperatureindicator 1032 and input keys 1036 are placed down adjacent to accesssleeve 1020 so they are below the bottom edge of the sterile drape andthus may be seen and accessed while the drape is in place.

An alternative to a passive control system where the heaters for thevertical access sleeves are always on but may be inadequate to bring thesterile fluid to the desired temperature if the ambient air temperatureis not unusually warm, is to provide an active control system for eachaccess sleeve. Under this mode of operation, each access sleeve (such as1020 and 1040) has a temperature sensor (not shown) that interacts witha controller (not shown) to regulate a heater (not shown) to attempt tobring the temperature sensed by that particular temperature sensorwithin a specific temperature range. The invention may be implementedwith each access sleeve controlled by a separate controller orimplemented with two or more of the access sleeves controlled by thesame controller.

As the precise temperature of the containers of sterile liquid is not asimportant as the temperature of the sterile liquid in the sterileremovable basin, some designers may choose to configure the liquidwarming device 1006 so that individual temperatures obtained from thetemperature sensors associated with each access sleeve are notexternally displayed. Further, while the target temperature for theaccess sleeves may be adjusted by calibration settings inside the liquidwarming device, the end user in the surgical room is not provided withan input means to adjust the target temperature for either theindividual access sleeves or the access sleeves as a group.

A Device with Access Sleeves but not a Heated Basin.

The examples discussed above have included a cavity for receiving aremovable basin and a heating system to heat sterile fluid place in theremovable basin. The advantages of having containers of sterile fluidmaintained at desired temperatures in the operating room may be obtainedthrough use of a access sleeve cabinet having a set of access sleeves.FIG. 10 shows access sleeve cabinet 1100 with thirty access sleeves1104. Fifteen access sleeves are visible in FIG. 10 and another fifteenaccess sleeves are on the opposite side of the access sleeve cabinet1100. Each access sleeve cavity 1112 is of sufficient size to receive abottle of sterile fluid. In this particular example, the access sleevebottoms are tilted towards the open side of the access sleeve and thusthese access sleeves have protrusions 1116. Each access sleeve has atemperature sensor (not shown) that obtains a temperature that isdisplayed on a corresponding temperature display 1108. The temperatureis used as an input for the control system regulating temperature ofthat access sleeve 1104. A countertop 1120 may be placed on the accesssleeve cabinet 1100 to provide a work surface outside of the sterilefield. Optionally, the access sleeve cabinet may include caster typewheels 1124 to allow the cabinet to be repositioned within the operatingsuite or to be wheeled over to a bulk heater cabinet to restock therolling access sleeve cabinet 1100.

Alternative Control System.

An alternative to the combination of heater cable assembly and controlsystem disclosed above is to use a cascade control scheme as illustratedin FIG. 11. A heater is used with excess capacity such that the heateris controlled by applying only a percentage of full power to the heater.The control system responds to the current temperature underage. Thetemperature underage is the difference between the target temperatureand the current temperature of the sterile fluid. If the targettemperature is set to 100 degrees Fahrenheit then a current temperatureof 90 degrees Fahrenheit for the container of sterile fluid wouldindicate a 10 degree temperature underage. Advantageously, the targettemperature may be modified by input keys or by other means, perhaps notby the individual users in the surgical suite but by those charged withthe duty of calibrating and maintaining the equipment.

The fluid temperature controller is set to operate the heater at amaximum temperature shown on FIG. 11 as temperature A. Choosing arelatively high temperature for temperature A quickly reduce thetemperature underage. However, it is prudent to choose a maximumtemperature that is well below the temperature that would damage theanticipated types of containers of sterile fluid. Another factor thatgoes into the selection of the maximum temperature is seeking to avoid asafety risk to the personnel using the access sleeves.

The steady state temperature shown as B on FIG. 11 is not a programmednumber but is the temperature of the heater that maintains the containerof the sterile fluid at the desired target temperature. The temperatureneeded to maintain the container of sterile fluid at a set point near100 degrees Fahrenheit will be slightly higher in an operating suitewith a lower ambient air temperature than in a similarly situatedoperating suite with a higher ambient air temperature. In order tooptimize responsiveness of the system, the maximum temperature is usedas the set point for the heater until the temperature of the containerof sterile fluid is relatively close to the target temperature. Forexample, the maximum temperature may be used until the temperatureunderage is only 2 degrees Fahrenheit.

As the temperature of the container of sterile fluid approaches thetarget temperature, the set point for the heater is reduced thus slowingthe rate of temperature increase of the sterile fluid. A suitable meansfor controlling the heater set point is the use of a standard PID(Proportional Integral Derivative) controller. An example of a suitablePID controller is a Series 988 Controller manufactured by Watlow ofWinona, Minn., www.watlow.com/products/controllers.

As the controller seeks to reduce the output of the heater, thecontroller operates a relay to reduce the percentage of time that theheater receives power. Thus, a heater maintaining a container of sterilefluid at the desired fluid temperature would be provided with power asmaller percentage of the time compared with the same heater bringingthe same container of fluid to the desired temperature as the latter isoperating at a higher set point temperature and the below temperaturecontainer of sterile fluid absorbs heat more readily.

Another implementation may remove the ability to adjust the targettemperature and would essentially have a fixed target temperature. Insuch a case, the heater set point would become a function of thetemperature of the container of sterile fluid as there would be aconsistent relationship between temperature of the container of sterilefluid and the temperature underage.

Alternative to Temperature Displays.

The temperature displays such as temperature displays 412 and 462 inFIG. 3 are one example of a means of providing feedback on thetemperature of the container of sterile fluid in the access sleeve.Other options exist including systems of two or more indicator lights asdescribed above in connection with the heated basin.

Convection Based System.

The example given above uses a temperature sensor with a thermallyconductive covering that contacts the side of the container of sterilefluid. An alternative is to measure the air temperature in the cavity ofthe access sleeve away from the open end of the access sleeve. Thistemperature will be influenced by the temperature of the container ofsterile fluid and eventually the temperature of the air and thetemperature of the container of fluid will converge. Such as systemwould allow two or more containers of fluid to be placed in the accesssleeve and the system may use convection rather than contact heat toconvey heat to the cavity and any containers held in the cavity of theaccess sleeve.

Liquid Heating Devices Not Using the Basin/Drape Combination ReferencedAbove.

Some of the examples given above have identified a basin holding sterilefluid that is kept warm by a heater. The basin is placed into a basincavity through an opening in a sterile drape so that the basin and thedrape form a protective barrier to isolate the sterile field from thedevice. While this is advantageous, it is not required for use of theinventive teachings with respect to access sleeves. One may place thesterile fluid directly into a cavity in the top of the device if thecavity and the top of the device were adequately sterilized for theintended use. One may place the sterile fluid in a sterile drape thatforms a draped cavity inside a cavity in the top of the device.Alternatively, one may place the sterile fluid in a sterile drape in abasin in a cavity in the top of the device.

V Configuration to Access Sleeve.

While the implementations described above have used a bottom wall of theopen access sleeve that was substantially horizontal in the axis runningperpendicular to the front to back axis, this is not a requirement ofthe invention. One of ordinary skill in the art may implement an openaccess sleeve for heated fluid units that has a V shape or curved shapeinstead of a flat bottom wall.

FIG. 12 shows an implementation that does not use a flat bottom wall. Abottle of fluid 1204 is placed inside access sleeve 1208 with a pair ofV-shaped walls 1212 and 1216 that support the bottle of fluid 1204. Thebottle of fluid 1204 may be made of material that allows the weight ofthe fluid to partially conform the shape of the bottle to the shape ofthe V-shaped walls. A temperature sensor 1220 may be placed adjacent toan opening in one of the pair of V-shaped walls and insulated from thewall so that when the bottle of fluid 1204 is placed in thermal contactwith the temperature sensor 1220, the temperature detected by thetemperature sensor 1220 may be used as an input to a control system toregulate a set of one or more heaters applying heat to the accesssleeve.

The slope of the centerline 1224 between the pair of V-shaped walls 1212and 1216 may be sloped towards the open end of the access sleeve topromote drainage of fluids and to cause the bottle to tend to restagainst one or more protrusions. The protrusions may protrude from oneor both of the pair if V-shaped walls. The protrusion may be arranged toextend from one of the walls to the other as shown with retainerprotrusion 1228.

An implementation using a pair of V-shaped walls where the centerline issubstantially horizontal from the front to the back of the access sleeveor slopes downward towards the back of the access sleeve may beimplemented without a protrusion in the front of the access sleeve.

The access sleeve may be implemented with other wall configurations thatsubstantially correspond to the shape of a portion of the primarycontainer used in the access sleeve. FIG. 13 is a front view of anaccess sleeve 1308 having a bottom surface 1312 with an arc that issimilar to the radius of bottles 1304 used in the access sleeve. Atemperature sensor 1320 may be placed adjacent to an opening in thebottom surface 1312 so that when the bottle 1304 is placed in thermalcontact with the temperature sensor 1320, the temperature obtained bythe temperature sensor 1320 may be used as an input to a control systemto regulate a set of one or more heaters applying heat to the accesssleeve. An implementation using a curved bottom wall may be slopedtowards the open front of the access sleeve and the bottle retained byone or more protrusions 1316. The bottom may be substantially horizontalalong the axis from the open front to the closed back of the accesssleeve or may have a downward slope that leads away from the open frontof the access sleeve.

One or skill in the art will recognize that the alternative embodimentsset forth above are not mutually exclusive and that in some casesalternative embodiments may be created that implement two or more of thevariations set forth above. For example, a dual-ended access sleeve maybe implemented with a pair of V-shaped walls and use convection heatingeven though that specific combination of features was not describedabove, but rather the individual features were introduced by discussionof specific illustrative implementations.

Section headers have been used to break up long stretches of text inorder to make it easier to find material relating to certain topics.These section headers are merely aids and do not impose limitations onthe interpretation of text found after that section heading.

Those skilled in the art will recognize that the methods and apparatusof the present invention have many applications and that the presentinvention is not limited to the specific examples given to promoteunderstanding of the present invention. Moreover, the scope of thepresent invention covers the range of variations, modifications, andsubstitutions for the system components described herein, as would beknown to those of skill in the art.

The legal limitations of the scope of the claimed invention are setforth in the claims that follow and extend to cover their legalequivalents. Those unfamiliar with the legal tests for equivalencyshould consult a person registered to practice before the patentauthority that granted this patent such as the United States Patent andTrademark Office or its counterpart

1. A liquid warming device for maintaining fluids used in the provisionof medical treatment at a temperature above ambient air temperature, theliquid warming device comprising: a first heating element adapted toapply heat to a volume of liquid to maintain the volume of liquid atapproximately a target temperature, the liquid warming device adapted tobe used with a volume of liquid that is not fully enclosed so that thevolume of liquid can be readily accessed by someone providing medicaltreatment; at least one access sleeve located within the liquid warmingdevice, the access sleeve open to ambient air at an open end and closedat an opposite end, the opposite end connected to the open end by a setof one or more walls running from the open end to the opposite end, anda second heating element in thermal contact with at least a portion ofthe set of walls of the at least one access sleeve, the second heatingelement responsive to a control system.
 2. The liquid warming device ofclaim 1 further comprising a first temperature sensing device in datacommunication with the control system used to regulate the operation ofthe second heating element in order to selectively apply heat to aclosed container of sterile fluid placed in the access sleeve.
 3. Theliquid warming device of claim 1 wherein the access sleeve slopes suchthat water placed on the access sleeve will flow towards the open end.4. The liquid warming device of claim 1 wherein the slope of a bottommost portion of the access sleeve surface between the opposite end andthe open end is substantially horizontal.
 5. The liquid warming deviceof claim 1 wherein the access sleeve between the opposite end and theopen end slopes downward towards the opposite end such that a closedcontainer of sterile fluid placed in the access sleeve tends to stay incontact with at least a portion of the opposite end.
 6. The liquidwarming device of claim 1 further comprising a protrusion extendingupward from the access sleeve near the open end of the access sleeve,the protrusion adapted to resist a closed container of sterile fluidsliding out the open end of the access sleeve.
 7. The liquid warmingdevice of claim 1 wherein the volume of liquid is contained in a basin.8. The liquid warming device of claim 1 wherein the volume of liquid iscontained in a cavity in the liquid warming device.
 9. The liquidwarming device of claim 1 wherein the volume of liquid is contained in adepression in a sterile drape.
 10. The liquid warming device of claim 1wherein the height of the access sleeve measured in the direction offloor to ceiling is less than the depth of the access sleeve measured inthe direction from the open end to the opposite end of the accesssleeve.
 11. The liquid warming device of claim 1 wherein the height ofthe access sleeve measured in the direction of floor to ceiling is morethan the depth of the access sleeve measured in the direction from theopen end to the opposite end of the access sleeve.
 12. The fluid warmingdevice of claim 2 wherein the temperature sensing device is placedadjacent to an opening in the set of walls such that a distal end of thetemperature sensing device is adapted to make thermal contact with aclosed container of sterile fluid placed in the access sleeve so thatthe temperature of the container can be used by the control system toregulate the operation of the second heating element in order toselectively apply heat to a closed container of sterile fluid placed inthe access sleeve.
 13. The liquid warming device of claim 2 wherein: thetemperature sensing device is placed in thermal contact with a portionof the set of walls that is adapted to provide thermal contact with aclosed container of sterile fluid placed in the access sleeve.
 14. Thefluid warming device of claim 2 wherein the first temperature sensingdevice measures the air temperature in the access sleeve and is adaptedto avoid direct thermal contact with a closed container of sterile fluidso that the air temperature in the access sleeve holding the closedcontainer of sterile fluid can be used by the control system to regulatethe operation of the second heating element in order to selectivelyapply heat to a closed container of sterile fluid.
 15. The fluid warmingdevice of claim 2 wherein the liquid warming device further comprises anindicator display adapted to indicate a temperature of a closedcontainer of sterile fluid in the access sleeve.
 16. The fluid warmingdevice of claim 15 wherein the indicator display provides a temperaturemeasured by the first temperature sensing device.
 17. The fluid warmingdevice of claim 15 wherein the indicator display provides an adjustedtemperature based on the temperature measured by the first temperaturesensing device.
 18. The fluid warming device of claim 15 wherein theindicator display provides at least two different visual indicationsincluding: one visual indication that the temperature measured by thefirst temperature sensing device is a temperature deemed suitable andfluid in the closed container of sterile fluid may be used in theprovision of medical treatment; and one visual indication that thetemperature measured by the first temperature sensing device is below aminimum temperature deemed suitable for use in the provision of medicaltreatment.
 19. The fluid warming device of claim 15 wherein theindicator display provides at least two different visual indicationscomprising: one visual indication that the temperature measured by thefirst temperature sensing device is a temperature deemed suitable andfluid in the closed fluid container may be used in the provision ofmedical treatment; and one visual indication that the temperaturemeasured by the first temperature sensing device is not at a temperaturedeemed suitable for use in the provision of medical treatment.
 20. Thefluid warming device of claim 1 further comprising an input device onthe exterior of the fluid warming device for conveying a user input toalter a set point used by the control system to regulate the operationof the second heating element in order to selectively apply heat to aclosed container of sterile fluid placed in the access sleeve.
 21. Thefluid warming device of claim 1 wherein a bottom-most surface in theaccess sleeve slopes downwards towards the open end of the access sleevewith a slope of not less than 5 degrees and not more than 15 degrees.22. The fluid warming device of claim 1 wherein a bottom-most surface inthe access sleeve slopes downwards towards the open end of the accesssleeve with a slope of not less than 1 degree.
 23. The fluid warmingdevice of claim 1 wherein a bottom-most surface in the access sleeveslopes downwards towards the open end of the access sleeve with a slopeof not less than 5 degrees and not more than 20 degrees.
 24. The fluidwarming device of claim 1 wherein the second heating element wrapsaround the set of walls that run from the open end to the opposite end.25. The fluid warming device of claim 1 wherein the second heatingelement comprises a self-regulating heating cable that decreases a heatoutput per linear foot of heating cable as a temperature of the heatingcable increases.
 26. The fluid warming device of claim 1 wherein thesecond heating element is responsive to a control system using a cascadecontrol scheme.
 27. A liquid warming device of claim 2 furthercomprising: a second access sleeve located within the liquid warmingdevice, the second access sleeve open to ambient air at an open end andclosed at an opposite end, the opposite end connected to the open end bya set of one or more walls running from the open end to the oppositeend; a third heating element in thermal contact with at least a portionof the set of walls of the second access sleeve, the third heatingelement responsive to a control system; and a second temperature sensingdevice in data communication with the control system used to regulatethe operation of the third heating element in order to selectively applyheat to a closed container of sterile fluid placed in the second accesssleeve.
 28. The liquid warming device of claim 27 wherein the controlsystem used to regulate the operation of the second heating element isthe same control system used to regulate the operation of the thirdheating element.
 29. A liquid warming device for maintaining fluids usedin the provision of medical treatment at a temperature above ambient airtemperature, the liquid warming device comprising: a first heatingelement adapted to apply heat to a volume of liquid to maintain thevolume of liquid at approximately a desired target temperature, thevolume of liquid not fully enclosed so that the volume of liquid can bereadily accessed by someone providing medical treatment; at least oneaccess sleeve located within the liquid warming device, the accesssleeve open to ambient air at an open end and closed at an opposite end,the opposite end connected to the open end by a set of one or more wallsrunning from the open end to the opposite end, the access sleeve havinga slope between the open end and the opposite end of sufficientmagnitude that water placed in the access sleeve will flow down towardsthe open end; a protrusion extending into the access sleeve from nearthe open end of the access sleeve, the protrusion used to resist thetendency of a closed container of sterile fluid to slide out of the openaccess sleeve; a second heating element in thermal contact with at leasta portion of the set of walls running from the open end to the oppositeend, the second heating element responsive to a control system; and afirst temperature sensing device in data communication with the controlsystem used to regulate the operation of the second heating element inorder to selectively apply heat to a closed container of fluid placed inthe open access sleeve.
 30. A dual-ended access sleeve for the provisionof heat to at least one closed container of sterile fluid, thedual-ended access sleeve comprising: an elongated cavity partiallydefined by a set of one or more walls running from a first open end atone end of the cavity to a second open end; the elongated cavity ofsufficient size to receive a first closed container of sterile fluid atthe first open end so that at least a base of the first closed containerof sterile fluid may be inserted into the elongated cavity and toreceive a second closed container of sterile fluid at the second openend so that at least a base of the second closed container may beinserted into the elongated cavity; a first temperature sensor placed inproximity to a portion of the set of one or more walls; a firstcontroller that receives input from the first temperature sensor andcontrols an amount of heat applied by the at least one first heater tothe dual-ended access sleeve.
 31. The dual-ended access sleeve of claim30 wherein the first temperature sensor is located in proximity to thefirst open end of the elongated cavity and the at least one first heaterapplies heat in proximity to a portion of the elongated cavity near thefirst open end; the dual-ended access sleeve further comprising: asecond temperature sensor placed in proximity a portion of the set ofone or more walls; a second controller that receives input from thesecond temperature sensor and controls an amount of heat applied by theat least one second heater and the at least one second heater appliesheat in proximity to a portion of the elongated cavity near the secondopen end.
 32. The dual-ended access sleeve of claim 31 furthercomprising: a first temperature indicator that displays a temperaturestatus of a measured temperature obtained by the first temperaturesensor and a second temperature indicator that displays a temperaturestatus of a measured temperature obtained by the second temperaturesensor.
 33. The dual-ended access sleeve of claim 32 wherein thetemperature status of the measured temperature obtained by the firsttemperature sensor is conveyed by displaying a temperature on a digitaldisplay.
 34. The dual-ended access sleeve of claim 32 wherein thetemperature status of the measured temperature obtained by the firsttemperature sensor is conveyed by an indicator light that provides anindication of whether the measured temperature is within a desiredtemperature range.
 35. The dual-ended access sleeve of claim 30 whereinthe dual-ended access sleeve is adapted so that a container inserted atthe first open end tends to slide away from the first open end towardsan interior of the dual-ended access sleeve and a container inserted inthe second open end tends to slide away from the second open end towardsthe interior of the dual-ended access sleeve.
 36. The dual-ended accesssleeve of claim 30 wherein the dual-ended access sleeve is adapted sothat a container inserted at the first open end tends to slide towardsthe first open end and a container inserted in the second open end tendsto slide towards the second open.
 37. The dual-ended access sleeve ofclaim 30 wherein the dual-ended access sleeve is adapted so that acontainer inserted at the first open end tends to slide away from thefirst open end towards the second open end and a container inserted inthe second open end tends to slide towards the second open end.
 38. Thedual-ended access sleeve of claim 30 further comprising a protrusionthat extends upward from a surface of the access sleeve near the firstopen end to resist the movement of a closed container of sterile fluidfrom inside the elongated cavity to outside the elongated cavity via thefirst open end.
 39. A method of maintaining a container of sterile fluidwithin a range of a target temperature, the method comprising: placing acontainer of sterile fluid in an open access sleeve in a position wherea temperature of the container of sterile fluid can be ascertained by atemperature measuring device connected to a control system, the controlsystem used to selectively apply power to a heating unit to increase thetemperature of the container of sterile fluid to a target temperature.40. The method of maintaining a container of sterile fluid within arange of a target temperature of claim 39 further including the step ofadjusting the target temperature through providing input to the controlsystem.
 41. The method of maintaining a container of sterile fluidwithin a range of a target temperature of claim 39 wherein the step ofplacing the container of sterile fluid in the open access sleeve isperformed by placing the container of sterile fluid on its side in anelongated cavity with an open front and the temperature measuring devicemeasures a temperature representative of a portion of a side of thecontainer of sterile fluid in contact with a portion of the open accesssleeve.
 42. The method of maintaining a container of sterile fluidwithin a range of a target temperature of claim 41 wherein the openaccess sleeve is sloped from a distal end of the access sleeve to theopen front of the access sleeve such that the container of sterile fluidrests against a protrusion near the open front of the access sleeve. 43.The method of maintaining a container of sterile fluid within a range ofa target temperature of claim 39 wherein a user seeking to use sterilefluid from within the container of sterile fluid waits until atemperature indicator indicates that the temperature of the container ofsterile fluid is within the range of the target temperature.
 44. Themethod of maintaining a container of sterile fluid within a range of atarget temperature of claim 43 where the temperature indicator is adigital indication of the temperature measured by the temperaturemeasuring device.
 45. The method of maintaining a container of sterilefluid within a range of a target temperature of claim 43 where thetemperature indicator is a light.
 46. The method of maintaining acontainer of sterile fluid within a range of a target temperature ofclaim 43 wherein a user opens the container of sterile fluid taken fromthe access sleeve and pours at least a portion of the sterile fluid fromthe container of sterile fluid into an open basin containing sterilefluid maintained within a range of a set point temperature.
 47. Themethod of maintaining a container of sterile fluid within a range of atarget temperature of claim 43 wherein the user opens the container ofsterile fluid taken from the access sleeve and pours at least a portionof the sterile fluid from the container of sterile fluid into a drapedcavity containing sterile fluid maintained within a range of a set pointtemperature.
 48. A method of slowing the cooling of sterile fluid in aclosed container of sterile fluid from an initial temperature T1 to theambient temperature of a room containing the closed container of sterilefluid, the method comprising: connecting a device having at least oneaccess sleeve to a power source to provide electric power to at leastone heater to heat at least a portion of the walls surrounding an accesssleeve; and placing the closed container of sterile fluid in the accesssleeve with at least one side of the access sleeve remaining open toambient air.
 49. The method of slowing the cooling of sterile fluid ofclaim 48 further including adjusting at least one internal settingwithin the device to alter the behavior of the at least one heater. 50.The method of slowing the cooling of sterile fluid of claim 48 whereinthe at least one heater operates without temperature feedback from atemperature sensor.
 51. The method of slowing the cooling of sterilefluid of claim 48 wherein the at least one heater operates in responseto a control system that receives a temperature measurement from atemperature sensor associated with the access sleeve.
 52. The method ofslowing the cooling of sterile fluid of claim 48 wherein the at leastone heater operates in response to a control system that receives atemperature measurement from a temperature sensor in contact with a wallof the access sleeve.
 53. The method of slowing the cooling of sterilefluid of claim 48 wherein the at least one heater operates in responseto a control system that receives a temperature measurement from atemperature sensor in contact with the closed container of sterile fluidplaced in the access sleeve.
 54. The method of slowing the cooling ofsterile fluid of claim 48 wherein the at least one heater operates inresponse to a control system that receives a temperature measurementfrom a temperature sensor in contact with air inside the access sleeve.55. The method of slowing the cooling of sterile fluid of claim 48wherein a controller response to a temperature input controls the atleast one heater to avoid heating the closed container of sterile fluidabove a target temperature.